Growth of a salt diapir in an anticline- A record from the Cenozoic halokinetic sequences in the Zagros Fold and Thrust Belt, Iran
Abstrakt
Salt diapirs in southern Iran provide excellent exposures of the host rock sedimentary sequences that record salt diapiric growth in compressional settings. This study addresses the reactivation of one particular diapir in the core of an anticline of the Zagros Fold and Thrust Belt (ZFTB) using the classical concept of halokinetic sequences.
These sequences reflect the relative rise of the salt diapirs with respect to the depositional rate of the sediments in their surroundings. The resulting reconstruction indicates irregular deposition of the total eight sets of host rock sedimentary packages around the diapir during the Oligocene-Miocene that developed in response to the progressive rise of the host anticline.
Folding of host rocks was associated with vertical movement of blocks bounded by cross-faults radiating from the boundary of the diapir, specifically around the triangular indenter on the north, deflecting the anticline to a southward advancing salient. The halokinetic sequences record an early stage of diapiric rise in the rhythmic alternation of gypsum and fossiliferous carbonate with siliciclastic material followed by fossiliferous limestone typical for lagoonal to slope environment in a limestone reef setting.
The last stage is associated with thin-skinned tectonics of the uppermost halokinetic sequences thrust towards the diapir. Rapid thickness change of the halokinetic strata along the periphery of the diapir in the southern sector that includes also the crestal region of the anticline indicates compressional reactivation of the structure as early as 11 Ma (Gachsaran Formation), likely associated with salt overflow in the anticline crestal region, where the adjacent halokinetic sequences are completely overturned.